Mobile station, method for controlling mobile station, mobile communication system, mobility management apparatus, and computer-readable medium

ABSTRACT

In one embodiment, a mobile station ( 1 ) is capable of performing location registration procedures with first and second mobile management units ( 31  and  32 ) that respectively correspond to first and second RANs (Radio Access Networks). Further, the mobile station ( 1 ) supports ISR (Idle mode Signalling reduction) for reducing location registration procedures caused by reselection between the first RAN ( 21 ) and the second RAN ( 22 ). Furthermore, the mobile station ( 1 ) is configured to deactivate ISR in the mobile station ( 1 ) when voice service configuration information stored in the mobile station ( 1 ) is updated when the ISR is activated.

TECHNICAL FIELD

The present invention relates to a location registration procedure for amobile station.

BACKGROUND ART

3GPP (3rd Generation Partnership Project) specifications define thefunction for reducing location registration procedures when a mobilestation makes reselection between different RANs (Radio Access Networks)provided by different RATs (Radio Access Technologies). This function isreferred to as ISR (Idle mode Signalling Reduction).

RAN covers a geographical area divided into a plurality of cells orsectors. Each cell or sector is provided by a base station. Specificexamples of RAN include UTRAN (Universal Terrestrial Radio AccessNetwork), GERAN (GSM EDGE Radio Access Network) and E-UTRAN (EvolvedUniversal Terrestrial Radio Access Network). A base station is referredto as NodeB, BTS (Base Transceiver Station) or eNodeB, for example.Further, a mobile station is referred to as UE (User Equipment) or MS(Mobile Station), for example.

The term “RAT” is used as synonymous with RAN in some cases; however, itis a concept that includes not only RAN but also a mobility managementnode or entity placed in a core network in general. Specific examples ofRAT include UTRA (Universal Terrestrial Radio Access) and E-UTRA(Evolved Universal Terrestrial Radio Access). E-UTRA is also called LTE(Long Term Evolution) in some cases. A mobility management node orentity in UTRA is SGSN (Serving GPRS Support Node). A mobilitymanagement node or entity in E-UTRA is MME (Mobility Management Entity).

Typically, the ISR can reduce signalling of location registrationprocedures when a mobile station in the idle state makes cellreselection between different RATs. The idle sate (or idle mode)generally means the following state. Specifically, in the idle state, amobile station is attached to a core network, and both of the mobilestation and the mobility management node (or entity) have MM contexts(or MM parameters). However, a NAS (Non Access Stratum) message is notsent and received between the mobile station and the mobility managementnode, and dedicated radio resources in the RAN are not allocated for themobile station. The core network keeps track of the location of themobile station in units of location registration area. The locationregistration area is called RA (Routing Area) in UTRA and called TA(Tracking Area) in E-UTRA. Note that, in E-UTRA, the mobile station canbelong to a plurality of TAs. In this case, the mobility management node(i.e., MME) keeps track of the location of the mobile station in unitsof TA list. The TA list can contain a plurality of TAs. Specificexamples of idle state include ECM (EPS Connection Management)-IDLEstate in E-UTRAN, PMM (Packet Mobility Management)-IDLE state in UTRANand GPRS-STANDBY state in GERAN. Further, specific examples of idlestate may include at least one of RRC_IDLE state in E-UTRAN, CELL_PCHstate and URA_PCH state in UTRAN, and Packet Idle state in GERAN.

When the mobile station frequently makes reselection between differentRANs, e.g., between E-UTRAN and GERAN/UTRAN, a location registrationprocedure is executed each time. The location registration procedure isreferred to as a location update procedure in some cases. The locationregistration procedure in E-UTRAN is TAU (Tracking Area Update). Thelocation registration procedure in GERAN/UTRAN is RAU (Routing AreaUpdate). The location registration procedure involves signalling betweenthe mobile station and the mobility management node located in the corenetwork and signalling in the core network. Signalling in the corenetwork includes, for example, signalling between the mobilitymanagement node and a subscriber server (e.g., HSS (Home SubscriberServer), HLR (Home Location Register)). Accordingly, frequent locationregistration procedures cause an increase in network load.

The ISR aims at reducing the location registration procedures caused byreselection between different RANs (Radio Access Networks). Currently,3GPP defines ISR for reselection by the mobile station between E-UTRANand GERAN/UTRAN. When the ISR is activated, the mobile station isregistered in both of the two mobility management nodes (or entities)corresponding to two RANs (or RATs). To be specific, the mobile stationis registered in both of the MME and the SGSN. Further, the mobilestation has both of the MM (Mobility Management) contexts received fromthe SGSN and the MM contexts received from the MME. The MM contexts fromthe SGSN contain P-TMSI (Packet-Temporary Mobile Subscriber Identity)and RAI (Routing Area Identity), for example. The P-TMSI is a temporaryidentifier assigned to the mobile station by the SGSN. The MM contextsfrom the MME contain GUTI (Globally Unique Temporary Identity) and TAI(Tracking Area Identity), for example. The GUTI is a temporaryidentifier assigned to the mobile station by the MME. When the ISR isactivated, the mobile station can make reselection between two RANs(i.e. GERAN/UTRAN and E-UTRAN) without performing a locationregistration procedure (i.e., RAU, TAU) unless it moves out of the twolocation registration areas (i.e. RA and TA(s)) registered in thenetwork.

The ISR is activated in the following procedure, for example. First, themobile station performs initial attach through either one of two RANs,i.e., through GERAN/UTRAN or E-UTRAN in this example. Here it isconsidered that the mobile station performs initial attach throughE-UTRAN. In the initial attach, the mobile station performs a locationregistration procedure with the MME, and the mobile station isregistered in the MME. The mobile station enters ECM-IDLE state.

Next, when the mobile station first reselects GERAN/UTRAN, the mobilestation initiates a location registration procedure (i.e., RAU).Specifically, the mobile station sends a RAU request to the SGSN. TheRAU request contains P-TMSI mapped from GUTI. The SGSN sends a contextrequest to the MME specified from the received GUTI. The SGSN therebysends the MM contexts (e.g., P-TMSI, RA) of the mobile station managedby itself to the MME, and receives the MM contexts (e.g., GUTI, TA(s))from the MME. Then, the SGSN sends a RAU accept. The RAU accept carriesthe MM contexts (e.g., P-TMSI, RA) and indicates “ISR activated”.

Upon receiving the RAU accept indicating “ISR activated”, the mobilestation activates the ISR in the own station. To be specific, the mobilestation sets its TIN (Temporary Identity used in Next update) to“RAT-related TMSI”. The TIN is one of the MM contexts held by the mobilestation. The TIN defines the identifier of the mobile station to bepresented by the mobile station in the next location registrationprocedure, i.e., RAU request, TAU request or attach request. As a resultof setting the TIN to “RAT-related TMSI”, the ISR operation in themobile station is started.

For overview of the ISR, refer to §4.3.5.6 “Idle mode signallingreduction function” and Annex J “High Level ISR description” in NonPatent Literature 1 (3GPP TS 23.401). The ISR is also described in NonPatent Literature 2 (3GPP TS 24.301) and Non Patent Literature 3 (3GPPTS 24.008).

Further, 3GPP specifications define a plurality of methods such as CSFallback and IMS Voice (Voice over IP) to provide a voice service to themobile station in E-UTRA. In relation to this, the network (e.g., MME)can indicate which RAN (or RAT) is to be selected preferentially whenthe mobile station that supports the voice service selects a cell. Forexample, “UEs usage setting” and “Voice domain preference for E-UTRAN”that are sent from the mobile station to the network may be used as anindex to determine the RAN (or RAT) to be selected preferentially. The“UEs usage setting” and “Voice domain preference for E-UTRAN” are storedin the mobile station and sent to the mobility management node (i.e.,MME, SGSN) by TAU request, RAU request and attach request.

The “UEs usage setting” indicates whether the mobile station behaves in“a voice centric” or “a data centric”. The “Voice domain preference forE-UTRAN” indicates whether the mobile station supports CS (CircuitSwitched) voice or PS (Packet Switched) voice and indicates which one ofCS voice and PS voice is more preferred. To be specific, the “Voicedomain preference for E-UTRAN” indicates the mobile station isconfigured as “CS Voice only”, “CS Voice preferred and IMS PS Voice assecondary”, “IMS PS Voice preferred and CS Voice as secondary” or “IMSPS Voice only”.

For overview of the “UEs usage setting” and “Voice domain preference forE-UTRAN”, refer to §4.3.5.9 “Voice domain preference and UE's usagesetting” and §4.3.6 “Radio Resource Management functions” in Non PatentLiterature 1 (3GPP TS 23.401), for example. The “UEs usage setting” and“Voice domain preference for E-UTRAN” are also described by Non PatentLiterature 2 (3GPP TS 24.301) in §3.1 “Definitions”, §4.3 “UE mode ofoperation”, §5.5.3.2.2 “Normal and periodic tracking area updatingprocedure initiation”, §5.5.3.3.2 “Combined tracking area updatingprocedure initiation” and the like. Further, they are described also byNon Patent Literature 3 (3GPP TS 24.008) in §4.7.5.1 “Normal andperiodic routing area updating procedure”, §4.7.5.2.1 “Combined routingarea updating procedure initiation” and the like.

In this specification, the term “voice service configurationinformation” is defined as information that is related to the priorityof a voice service stored in the mobile station and that is sent fromthe mobile station to the network and used in the network as an indexfor selecting RAN (or RAT) which provides a voice service to the mobilestation, such as the above-described “UEs usage setting” and “Voicedomain preference for E-UTRAN”.

CITATION LIST Non Patent Literature

[Non Patent Literature 1] 3GPP TS 23.401 V11.0.0 (2011 December),“General Packet Radio Service (GPRS) enhancements for Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) access”, 3GPP (3rd GenerationPartnership Project, December 2011

[Non Patent Literature 2] 3GPP TS 24.301 V11.1.0 (2011 December),“Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS);Stage 3”, 3GPP (3rd Generation Partnership Project), December 2011

[Non Patent Literature 3] 3GPP TS 24.008 V11.1.2 (2012 January), “Mobileradio interface Layer 3 specification; Core network protocols; Stage 3”,3GPP (3rd Generation Partnership Project), January 2012

SUMMARY OF INVENTION Technical Problem

When the voice service configuration information such as theabove-described “UEs usage setting” and “Voice domain preference forE-UTRAN” are updated in the mobile station, the mobile station performsa location registration procedure with the mobility management node(e.g., MME or SGSN) corresponding to the currently selected RAN, therebyinforming the mobility management node about the update of the voiceservice configuration information. To be specific, the mobile stationsends a TAU request or a RAN request indicating the update of the voiceservice configuration information. The mobility management nodecorresponding to the currently selected RAN can thereby recognize theupdate of the voice service configuration information.

However, the update of the voice service configuration information, suchas the above-described “UEs usage setting” and “Voice domain preferencefor E-UTRAN” in the mobile station, is not used as a trigger fordeactivation of the ISR. Accordingly, when the ISR is activated, themobile station does not initiate the location registration procedureduring reselection of RAN that is performed after the update of thevoice service configuration information. Therefore, the mobilitymanagement node corresponding to the reselected RAN cannot recognize theupdate of the voice service configuration information. This means thatselection of RAN (or RAT) different from the expectation of the mobilestation may occur at the reselected RAN. For example, there is apossibility that the mobile station is forced to move to other RANwithout conforming to the priority assumed from the updated voiceservice configuration information.

That is, when the voice service configuration information stored in themobile station is updated when the ISR is activated, discrepancy in thecontents of the voice service configuration information can arisebetween mobility management nodes (e.g., MME and SGSN) where the ISR isactivated.

The present invention has been accomplished based on the above-describedfinding by the present inventor and an object of the present inventionis thus to provide a mobile station, a method for controlling a mobilestation, a mobile communication system, a mobility management apparatus,and a program that can contribute to solve the problem of discrepancy inthe contents of the voice service configuration information describedabove.

Solution to Problem

A first aspect includes a mobile station. The mobile station includes acommunication control unit. The communication control unit is capable ofperforming location registration procedures with first and secondmobility management units respectively corresponding to first and secondRANs (Radio Access Networks) and supports ISR (Idle mode SignallingReduction) for reducing location registration procedures caused byreselection between the first and second RANs by the mobile station.Further, when voice service setting information stored in the mobilestation is updated when the ISR is activated, the communication controlunit deactivates the ISR in the mobile station.

A second aspect includes a method for controlling a mobile station thatcan be registered in both of first and second mobility management unitsrespectively corresponding to first and second RANs (Radio AccessNetworks) and supports ISR (Idle mode Signalling Reduction) for reducinglocation registration procedures caused by reselection between the firstand second RANs. The method includes, when voice service configurationinformation stored in the mobile station is updated when the ISR isactivated, deactivating the ISR in the mobile station.

A third aspect includes a mobile communication system. The mobilecommunication system includes first and second mobility management unitsrespectively corresponding to first and second RANs and a mobilestation. The mobile station is capable of performing locationregistration procedures with the first and second mobility managementunits and supports ISR (Idle mode Signalling Reduction) for reducinglocation registration procedures caused by reselection between the firstand second RANs by the mobile station. Further, the mobile station isconfigured to deactivate the ISR in the mobile station when voiceservice configuration information stored in the mobile station isupdated when the ISR is activated.

A fourth aspect includes a mobility management apparatus. The mobilitymanagement apparatus supports ISR (Idle mode Signalling Reduction) forreducing location registration procedures caused by reselection betweenfirst and second RANs by a mobile station. The mobility managementapparatus includes an ISR control unit that sends a locationregistration response indicating deactivation of the ISR to the mobilestation in response to receiving, from the mobile station when the ISRis activated, a location registration request indicating update of voiceservice configuration information stored in the mobile station.

A fifth aspect includes a program that causes a computer to perform themethod according to the second aspect described above.

Advantageous Effects of Invention

According to the above-described aspects, it is possible to provide amobile station, a method for controlling a mobile station, a mobilecommunication system, a mobility management apparatus, and a programthat can contribute to solve the problem of discrepancy in the contentsof the voice service configuration information described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration example of a mobilecommunication system according to a first embodiment.

FIG. 2 is a block diagram showing a configuration example of a mobilestation according to the first embodiment.

FIG. 3 is a sequence chart showing a relationship between update ofvoice service configuration information VSC and location registrationprocedure when ISR is activated according to the first embodiment.

FIG. 4 is a sequence chart of a comparative example showing arelationship between update of voice service configuration informationVSC and location registration procedure when the ISR is activated.

FIG. 5 is a sequence chart showing a relationship between update ofvoice service configuration information VSC and location registrationprocedure when the ISR is activated according to a second embodiment.

FIG. 6 is a block diagram showing a configuration example of SGSNaccording to the second embodiment.

FIG. 7 is a flowchart showing an operation example of SGSN whenreceiving a RAU request according to the second embodiment.

FIG. 8 is a sequence chart showing a relationship between update ofvoice service configuration information VSC and location registrationprocedure when the ISR is activated according to a third embodiment.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the present invention will be describedhereinafter in detail with reference to the drawings. It is noted thatin the description of the drawings, the same elements will be denoted bythe same reference symbols and redundant description will be omitted toclarify the explanation.

First Embodiment

FIG. 1 shows a configuration example of a mobile communication systemaccording to this embodiment. This embodiment describes a combinedsystem of 3GPP UMTS and EPS (Evolved Packet System). In other words, themobile communication system according to this embodiment providesdifferent RANs (i.e., an E-UTRAN 21 and a GERAN/UTRAN 22) and supportsthe above-described ISR (Idle mode Signalling Reduction).

In the example of FIG. 1, the mobile communication system includes acore network 3 and a mobile station 1. The core network 3 includes anMME 31 and an SGSN 32. The MME 31 is a mobility management node (orentity) corresponding to the E-UTRAN 22. The SGSN 32 is a mobilitymanagement node (or entity) corresponding to the GERAN/UTRAN 22. Notethat, this embodiment mainly describes the control plane functions,i.e., mobility management and the ISR for the mobile station 1. Thus,the SGSN 32 of FIG. 1 may have the control plane functions only. The MME31 and the SGSN 32 both support the ISR, and can send and receive acontext related to the mobile station 1 containing the voice serviceconfiguration information received from the mobile station 1 with eachother, thereby synchronizing the contexts with each other. Signallingfor sending and receiving the context may be performed using aninterface (i.e., S3 Interface) available between the MME 31 and the SGSN32.

As already indicated above, the voice service configuration informationis information that is related to the priority of a voice service storedin the mobile station 1 and that is sent from the mobile station 1 tothe core network 3 and used in the core network 3 as an index forselecting RAN (or RAT) which provides a voice service to the mobilestation 1. The voice service configuration information includes, forexample, at least one of the above-described “UEs usage setting” and“Voice domain preference for E-UTRAN”.

Although not shown in FIG. 1, the core network 3 may include a transfernode (or entity) in a user plane as a matter of course. The transfernode (or entity) performs transfer (e.g., routing or forwarding) of userdata. The core network 3 may include a plurality of transfer nodes (orentities). In the case of EPS, the transfer node (or entity) includes anS-GW (Serving Gateway) and a P-GW (Packet Data Network Gateway). In thecase of UMTS, the transfer node (or entity) includes the user planefunction of an SGSN and the user plane function of a GGSN (Gateway GPRSSupport Node). Thus, the core network 3 may include an EPC (EvolvedPacket Core) corresponding to LTE and a GPRS (General Packet RadioService) packet core for UMTS.

The mobile station 1 is a dual mode terminal that supports a pluralityof RATs, which are E-UTRA and UTRA in this example. In other words, themobile station 1 is capable of establishing a connection to the E-UTRAN21 through LTE wireless access and a connection to the GERAN/UTRAN 22through 2G/3G wireless access. The mobile station 1 in the idle state(e.g., ECM-IDLE state, PMM-IDLE state or GPRS-STANDBY state) can makereselection (cell reselection) between the E-UTRAN 21 and theGERAN/UTRAN 22. When selecting the E-UTRAN 21, the mobile station 1performs TAU procedure as the location registration procedure. On theother hand, when selecting the GERAN/UTRAN 22, the mobile station 1performs RAU procedure as the location registration procedure. The TAUprocedure includes sending a TAU request from the mobile station 1 tothe MME 31 and sending a TAU accept from the MME 31 to the mobilestation 1. On the other hand, the RAU procedure includes sending a RAUrequest from the mobile station 1 to the SGSN 32 and sending a RAUaccept from the SGSN 32 to the mobile station 1.

The mobile station 1 supports the ISR for reducing signalling related tothose location registration procedures. Specifically, when the ISR isactivated after the mobile station 1 is registered in both of the MME 31and the SGSN 32, the mobile station can make reselection between twoRANs (i.e., the E-UTRAN 21 and the GERAN/UTRAN 22) without performingthe a location registration procedure (i.e., RAU, TAU) unless it movesout of the two location registration areas (i.e., RA and TA(s))registered in the network.

Note that, however, the mobile station 1 according to the firstembodiment is configured to deactivate the ISR in the mobile station 1when the voice service configuration information stored in the mobilestation 1 is updated when the ISR is activated. The ISR deactivation inthe mobile station 1 may be local ISR deactivation in the mobile station1. In other words, even when an instruction from the network (i.e., theMME 31 and the SGSN 32) indicates “ISR activated”, the mobile station 1may spontaneously and locally deactivate the ISR in the mobile station 1without depending on the instruction from the network.

The local ISR deactivation in the mobile station 1 is done by changingthe TIN (Temporary Identity used in Next update) from “RAT-related TMSI”to GUTI or P-TMSI. Whether the TIN is set to GUTI or P-TMSI isdetermined according to the RAN selected by the mobile station 1. To bespecific, when the mobile station 1 selects the E-UTRAN 21, the mobilestation 1 sets the TIN to GUTI for ISR deactivation. On the other hand,when the mobile station 1 selects the GERAN/UTRAN 22, the mobile station1 sets the TIN to P-TMSI for ISR deactivation.

Further, instead of spontaneous and local ISR deactivation by the mobilestation 1, the ISR deactivation in the mobile station 1 caused byupdating the voice service configuration information may be performedaccording to an instruction for deactivation from the MME 31 or the SGSN32. This example is described in detail in the second embodiment below.

With the spontaneous and local ISR deactivation by the mobile station 1,there is an advantage that it is possible to solve the problem ofdiscrepancy in the contents of the voice service configurationinformation without adding new functions to the mobility managementnodes (or entities) on the network side, i.e., the MME 31 and the SGSN32. The MME 31 and the SGSN 32 only need to perform the normal ISRoperation specified in the current 3GPP specifications. On the otherhand, in the case of performing ISR deactivation in the mobile station 1according to an instruction for deactivation from the MME 31 or the SGSN32, there is an advantage that it is possible to solve the problem ofdiscrepancy in the contents of the voice service configurationinformation without adding new functions to the mobile station 1. Themobile station 1 only needs to deactivate the ISR state of itself inaccordance with the normal ISR operation specified in the current 3GPPspecifications.

The ISR deactivation in the mobile station 1 causes the mobile stationto perform the location registration procedure (i.e., TAU or RAU) withone of the MME 31 and the SGSN 32 corresponding to a RAN to which themobile station 1 moves during reselection of RAN that is performed afterthe update of the voice service configuration information. This isbecause, as a result that the ISR is deactivated, the mobile station 1cannot skip the location registration procedure and has to perform thelocation registration procedure (i.e., TAU or RAU) with one of the MME31 and the SGSN 32 corresponding to the reselected RAN to which themobile stations moves.

Hereinafter, a scheme that the updated content of the voice serviceconfiguration information in the mobile station 1 is synchronizedbetween the MME 31 and the SGSN 32 by the ISR deactivation in the mobilestation 1 is described. The synchronization can be achieved by any ofthe following two examples:

-   -   (Example 1) Exchanging a context between the MME 31 and the SGSN        32, or    -   (Example 2) Sending, from the mobile station 1 to both of the        MME 31 and the SGSN 32, a notification of the update of the        voice service configuration information.

Those two examples are sequentially described below.

Example 1

The example 1 corresponds to the case where the mobile station 1actually deactivates the ISR in an explicit manner and informs the MME31 or the SGSN 32 about the ISR deactivation. To be specific, the mobilestation 1 locally deactivates the ISR by actually changing the TIN from“RAT-related TMSI” to GUTI or P-TMSI. The mobile station 1 therebyperforms a location registration procedure with the mobility managementnode (e.g., the MME 31) corresponding to the RAN to be reselected (theRAN to which it moves) during RAN reselection that is performed afterthe ISR deactivation in the mobile station 1. In this locationregistration procedure, the mobile station 1 sends a locationregistration request (e.g., a TAU request) indicating ISR deactivated.The ISR deactivated is indicated by the fact that a temporary identifier(TMSI) of the mobile station 1 contained in the TAU request and the RAUrequest is GUTI or P-TMSI, not “RAT-related TMSI”. According to a normalprocedure when ISR is deactivated, the mobility management node (e.g.,the MME 31), which has received the location registration requestindicating that the ISR is deactivated in the mobile station 1, requestsa context related to the mobile station 1 to the other mobilitymanagement node (e.g., the SGSN 32) and receives it from the othermobility management node. Thus, the context related to the mobilestation 1 containing the voice service configuration information isresynchronized between the MME 31 and the SGSN 32.

Note that, as is already described earlier, the mobile station 1 hasperformed a location registration procedure with the mobility managementnode (e.g., the SGSN 32) corresponding to the RAN before reselection(the RAN from which it moves) prior to the location registrationprocedure and the context resynchronization after the RAN reselectiondescribed above. Specifically, when the voice service configurationinformation is updated in the mobile station 1 when the ISR isactivated, the mobile station 1 performs a location registrationprocedure with the mobility management node (e.g., the SGSN 32)corresponding to the currently selected RAN. The mobility managementnode (e.g., the SGSN 32) is thereby notified of the update of the voiceservice configuration information.

Accordingly, in the example 1, the context containing the updated voiceservice configuration information that has been sent to one mobilitymanagement node (e.g., the SGSN 32) in advance is transferred to theother mobility management node (e.g., the MME 31), triggered by thelocation registration request after ISR deactivation. The updatedcontent of the voice service configuration information in the mobilestation 1 is thereby synchronized between the MME 31 and the SGSN 32.

Example 2

The example 2 corresponds to the case where the mobile station 1 doesnot inform the MME 31 and the SGSN 32 about ISR deactivation. Stateddifferently, the mobile station 1 deactivates the ISR in an implicitmanner. In this case, the mobile station 1 does not need to explicitlyperform local ISR deactivation. The mobile station 1 thereby does notneed to change the TIN. In the example 2, the mobile station 1 informsboth of the MME 31 and the SGSN 32 about the update of the voice serviceconfiguration information. To be more specific, the mobile station 1 maysend a location registration request indicating the update of the voiceservice configuration information to both of the MME 31 and the SGSN 32.

As is already described earlier, when the voice service configurationinformation is updated in the mobile station 1 when the ISR isactivated, the mobile station 1 performs a location registrationprocedure with the mobility management node (e.g., the SGSN 32)corresponding to the currently selected RAN. The mobility managementnode (e.g., the SGSN 32) is thereby notified of the update of the voiceservice configuration information. To be specific, the mobile station 1sends a location registration request (e.g., a RAU request) indicatingthe update of the voice service configuration information. The mobilitymanagement node (e.g., the SGSN 32) corresponding to the currentlyselected RAN can thereby recognize the update of the voice serviceconfiguration information.

Further, in the example 2, the mobile station 1 sends a locationregistration request indicating the update of the voice serviceconfiguration information also to the mobility management node (e.g.,the MME 31) corresponding to the RAN to be reselected (the RAN to whichit moves). The mobility management node (e.g., the MME 31) correspondingto the RAN to be reselected (the RAN to which it moves) can thereby alsorecognize the update of the voice service configuration information.Accordingly, the updated content of the voice service configurationinformation in the mobile station 1 is synchronized between the MME 31and the SGSN 32.

The example 2 is significant in that the mobile station 1 does not needto inform the network (the MME 31 and the SGSN 32) about ISRdeactivation. Further, the MME 31 and the SGSN 32 can synchronize theupdated content of the voice service configuration information in themobile station 1 with each other without signalling for contextresynchronization. Note that, however, the example 1 has an advantagethat the impact of a specification change is smaller compared to theexample 2. This is because, in the example 2, the mobile station 1 isrequested to perform an operation which is different from local ISRactivation/deactivation in the mobile station that is specified in thecurrent 3GPP specifications.

As described above, when the voice service configuration informationstored in the mobile station 1 is updated when the ISR is activated, themobile station 1 deactivates the ISR in the mobile station 1. By the ISRdeactivation, a location registration procedure is performed between themobile station 1 and the mobility management node (e.g., the MME 31 orthe SGSN 32) corresponding to a RAN to which the mobile station 1 moves,at the time of RAN reselection that is performed after the update of thevoice service configuration information. Then, based on the locationregistration procedure, the updated content of the voice serviceconfiguration information in the mobile station 1 is synchronizedbetween the MME 31 and the SGSN 32. As described above, thesynchronization of the updated voice service configuration informationbetween the MME 31 and the SGSN 32 may be achieved by contextsynchronization between the MME 31 and the SGSN 32 which is triggered bythe location registration procedure between the mobile station 1 and themobility management node to which it moves. Alternatively, thesynchronization of the updated voice service configuration informationbetween the MME 31 and the SGSN 32 may be achieved by sending anotification of the update of the voice service configurationinformation from the mobile station 1 during the location registrationprocedure between the mobile station 1 and the mobility management nodeto which it moves.

Hereinafter, a configuration example of the mobile station 1 isdescribed. Further, an example of the procedure to synchronizing,between the MME 31 and the SGSN 32, the voice service configurationinformation updated in the mobile station 1 is described. FIG. 2 is ablock diagram showing a configuration example of the mobile station 1.Note that FIG. 2 shows only the major components related to the locationregistration procedure, the ISR and the update of the voice serviceconfiguration information according to this embodiment.

The configuration example of FIG. 2 includes a radio communication unit10 and a communication control unit 11. The radio communication unit 10is capable of connecting to a plurality of RANs, which are the E-UTRAN21 and the GERAN/UTRAN 22 in this example. The radio communication unit10 receives a downlink signal containing a plurality of physicaldownlink channels from a base station included in the E-UTRAN 21 or theGERAN/UTRAN 22. Further, the radio communication unit 10 transmits anuplink signal containing a plurality of physical uplink channels to abase station.

The communication control unit 11 performs signalling with the E-UTRAN21, the GERAN/UTRAN 22 and the core network 3 through the radiocommunication unit 10 and controls the radio communication unit 10 forsending and receiving control data and user data. Further, thecommunication control unit 11 performs digital baseband signalprocessing on the control data and user data. The digital basebandsignal processing includes layer-2 signal processing and layer-1(physical layer) signal processing. The layer-2 signal processingincludes, for example, data compression/decompression and datasegmentation/concatenation. The physical layer signal processingincludes, for example, channel coding/decoding andmodulation/demodulation.

In the example of FIG. 2, the communication control unit 11 includes anLTE control unit 111 and a 2G/3G control unit 112. The LTE control unit111 performs communication control for connecting to LTE, i.e., theE-UTRAN 21 and the EPC (e.g., the MME 31). On the other hand, the 2G/3Gcontrol unit 112 performs communication control for connecting to UMTS,i.e., the GERAN/UTRAN 22 and the GPRS packet core (e.g., the SGSN 32).

The communication control unit 11 performs communication controlincluding the location registration procedure, the processing related tothe ISR and the update of the voice service configuration informationdescribed earlier. Thus, in the case where the voice serviceconfiguration information VSC stored in the mobile station 1 is updatedwhen the ISR is activated, the communication control unit 11 deactivatesthe ISR in the mobile station 1.

The functions of the communication control unit 11 may be implementedusing a semiconductor processing device including ASIC (ApplicationSpecific Integrated Circuit), DSP (Digital Signal Processor) and thelike. Further, the functions of the communication control unit 11 may beimplemented by causing a computer such as a microprocessor to execute aprogram. Furthermore, the functions of the communication control unit 11may be implemented by any combination of ASIC, DSP and a microprocessor.For example, at least part of the digital baseband signal processing maybe performed in a DSP, and the other processing (e.g., the locationregistration procedure, the processing related to the ISR and the updateof the voice service configuration information) may be performed in amicroprocessor.

As described above, at least some of the functions of the communicationcontrol unit 11 may be implemented by causing a computer such as amicroprocessor to execute a program. The program can be stored andprovided to the computer using any type of non-transitory computerreadable medium. The non-transitory computer readable medium includesany type of tangible storage medium. Examples of the non-transitorycomputer readable medium include magnetic storage media (such as floppydisks, magnetic tapes, hard disk drives, etc.), optical magnetic storagemedia (e.g. magneto-optical disks), CD-ROM (Read Only Memory), CD-R,CD-R/W, and semiconductor memories (such as mask ROM, PROM (ProgrammableROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory),etc.). The program may be provided to a computer using any type oftransitory computer readable medium. Examples of the transitory computerreadable medium include electric signals, optical signals, andelectromagnetic waves. The transitory computer readable medium canprovide the program to a computer via a wired communication line such asan electric wire or optical fiber or a wireless communication line.

FIG. 3 is a sequence chart showing one example of the procedure toachieve synchronization of the voice service configuration informationVSC updated in the mobile station 1 between the MME 31 and the SGSN 32.The example of FIG. 3 begins with the state where the mobile station 1is already registered in both of the MME 31 and the SGSN 32, and the ISRis activated (Step S101). Further, the mobile station 1, the MME 31 andthe SGSN 32 store the same voice service configuration information VSCas a part of the context related to mobility management (Steps S102 toS105). It is assumed that the value of the voice service configurationinformation VSC is “A”. The mobile station 1 in the idle state selectsthe GERAN/UTRAN 22 (Step S105).

In Step S106, the voice service configuration information VSC stored inthe mobile station 1 is updated from the value “A” to the value “B” byan instruction from, for example, a user. In Step S107, thecommunication control unit 11 (i.e. the 2G/3G control unit 112) of themobile station 1 sends a RAU request to the SGSN 32 corresponding to thecurrently selected GERAN/UTRAN 22. This RAU request contains anotification about the update of the voice service configurationinformation VSC. Upon receiving the RAU request, the SGSN 32 updates thevoice service configuration information VSC stored for the mobilestation 1 to the notified value “B” (Step S108). In Step S109, the SGSN32 sends a RAU accept to the mobile station 1.

The RAU accept sent in Step S109 indicates whether the ISR is activatedor not. In the example of FIG. 3, the RAU accept sent in Step S109indicates “ISR activated”. However, regardless of an instruction of theRAU accept, the mobile station 1 (i.e. the communication control unit11) spontaneously deactivates the ISR in the mobile station 1 even whenthe RAU accept indicates “ISR activated” (Step S110). As is alreadydescribed above, the spontaneous and local ISR deactivation in themobile station 1 is achieved by changing the value of TIN from“RAT-related TMSI” to GUTI, for example, regardless of an instruction ofthe RAU accept.

Note that the ISR deactivation in the mobile station 1 is performedbefore or during RAN reselection occurring after the update of the voiceservice configuration information VSC. For example, the communicationcontrol unit 11 may deactivate the ISR in the mobile station 1 inresponse to receiving the RAU accept in Step S109, regardless of aninstruction of the RAU accept, and continue the deactivated state untilthe next RAN selection. Alternatively, the communication control unit 11may continue the ISR activated state, when receiving the RAU accept inStep S109, according to an instruction of the RAU accept. In this case,the communication control unit 11 may memorize the occurrence of theupdate of the voice service configuration information and deactivate theISR in the mobile station 1 at the future RAN reselection.

In Step S111, the mobile station 1 (i.e., the communication control unit11) in the idle state determines to move from the GERAN/UTRAN 22 to theE-UTRAN 21 (i.e., cell reselection). This cell reselection is Inter-RATcell reselection. At this time, the ISR is deactivated in the mobilestation 1. Thus, in Step S112, the communication control unit 11 (i.e.,the LTE control unit 111) of the mobile station 1 sends a TAU request tothe MME 31 corresponding to the E-UTRAN 21 to which it moves. This TAUrequest indicates that the ISR is deactivated in the mobile station 1.To be specific, a temporary identifier of the mobile station 1 containedin the TAU request is set to “GUTI mapped from P-TMSI”.

Because the TAU request indicates ISR deactivated in the mobile station1, the MME 31 carries out a procedure to restart the ISR with the SGSN32 (Steps S113, S114). Specifically, the MME 31 sends a context requestrelated to the mobile station 1 to the SGSN 32 and receives a contextresponse from the SGSN 32. The context related to the mobile station 1that is sent by the context response contains the updated voice serviceconfiguration information VSC (the value “B”). Thus, the MME 31 updatesthe voice service configuration information VSC for the mobile station1, which have stored by the MME 31, to the notified value “B” (StepS115). The voice service configuration information VSC updated in themobile station 1 is thereby synchronized between the MME 31 and the SGSN32.

FIG. 3 shows the example where the voice service configurationinformation VSC is updated in the mobile station 1 when the GERAN/UTRAN22 is selected, and then the mobile station 1 reselects the E-UTRAN 21after that. On the contrary, in the case where the voice serviceconfiguration information VSC is updated in the mobile station 1 whenthe E-UTRAN 21 is selected, and then the mobile station 1 reselects theGERAN/UTRAN 22 also, the synchronization of the voice serviceconfiguration information VSC can be performed in the same procedure asshown in FIG. 3.

Comparative Example

A comparative example is described hereinafter with reference to FIG. 4.FIG. 4 shows a procedure without performing an operation to deactivatethe ISR in the mobile station 1 triggered by the update of the voiceservice configuration information when the ISR is activated. In FIG. 4,reference symbols for the mobile station and the core network aredifferentiated in order to clarify differences from this embodiment. Theoperations of a mobile station 91 (including a LTE control unit 9111 anda 2G/3G control unit 9112) and a core network 93 (including an MME 931and an SGSN 932) in Steps S101 to S109 in FIG. 4 are the same as StepsS101 to S109 shown in FIG. 3.

However, in Step S910, the mobile station 91 maintains the ISR activatedstate according to an instruction of the RAU accept in Step S109.Specifically, the value of the TIN remains “RAT-related TMSI” whichcorresponds to ISR activated. Accordingly, when the E-UTRAN 21 isselected in Inter-RAT cell reselection in Step S111, the mobile station91 does not initiate an operation to send a TAU request because the ISRis activated in the mobile station 91 (Step S912). Discrepancy in thecontents of the voice service configuration information VSC therebyarises between the MME 31 and the SGSN 32.

If discrepancy in the contents of the voice service configurationinformation VSC arises between the MME 31 and the SGSN 32, the followingdisadvantage will occur. For example, one possible disadvantage is thatthe mobility management node (e.g., the MME 931), which has the voiceservice configuration information VSC before update, or a base stationcontrolled by the mobility management node indicates the priority of theRAN (or RAT) to the mobile station 91 based on the voice serviceconfiguration information VSC before update. This can cause that themobile station 91 is requested to select the RAN (or RAT) that is notsuitable for the voice service configuration information VSC afterupdate. As an example, despite that the mobile station 91 supports IMSVoice (Voice over IP), the mobile station 91 is instructed topreferentially select the GERAN/UTRAN 22, not the E-UTRAN 21. In thiscase, the mobile station 91 misses an opportunity to use a high-speedpacket service by the LTE (the E-UTRAN 21 and the EPC).

Another possible disadvantage is that the MME 931 and the SGSN 932 wherediscrepancy arises indicate different priorities to the E-UTRAN 21 andthe GERAN/UTRAN 22. This can cause that the mobile station 91 frequentlyrepeats reselection between the E-UTRAN 21 and the GERAN/UTRAN 22. Inthis case, the mobile station 91 suffers from heavy battery consumption.

On the other hand, the embodiment described with reference to FIGS. 1 to3 can prevent the occurrence of discrepancy in the contents of the voiceservice configuration information between the mobile station 1 and aplurality of mobility management nodes corresponding to different RATs(e.g., the MME 31 and the SGSN 32). Accordingly, it is possible toprevent the disadvantages assumed in the comparative example of FIG. 4.

Second Embodiment

The first embodiment describes several examples of the procedure todeactivate the ISR in the mobile station 1 in response to the update ofthe voice service configuration information in the mobile station 1. Thesecond embodiment describes one of those examples in detail. To bespecific, the second embodiment describes the example in which ISRdeactivation in the mobile station 1 is performed in response toreceiving an instruction for deactivation from the MME 31 or the SGSN32. Note that the configuration of the mobile communication systemaccording to the second embodiment may be the same as the configurationexample shown in FIG. 1.

FIG. 5 is a sequence chart showing one example of the procedure toachieve synchronization of the voice service configuration informationVSC updated in the mobile station 1 between the MME 31 and the SGSN 32.FIG. 5 is different from FIG. 3 in Steps S209 and S210.

In the example of FIG. 5, the SGSN 32, which has received a RAU requestcontaining a notification about the update of the voice serviceconfiguration information VSC, determines that the ISR should bedeactivated. Then, in Step S209, the SGSN 32 sends a RAU accept notcontaining an instruction of ISR activation (stated differently, a RAUaccept indicating ISR deactivated) to the mobile station 1. In StepS210, the mobile station 1 deactivates the ISR in the mobile station 1according to an instruction from the SGSN 32 indicated by the RAUaccept.

Note that, the synchronization of the voice service configurationinformation VSC can be performed in the same procedure as shown in FIG.5 also in the case where the voice service configuration information VSCis updated in the mobile station 1 when the E-UTRAN 21 is selected, andthen the mobile station 1 reselects the GERAN/UTRAN 22 after that.

According to the example shown in FIG. 5, it is possible to solve theproblem of discrepancy in the contents of the voice serviceconfiguration information without adding new functions to the mobilestation 1. The mobile station 1 only needs to deactivate the ISR stateof itself according to the normal ISR operation specified in the current3GPP specifications.

FIG. 6 is a block diagram showing a configuration example of the SGSN 32according to this embodiment. Note that FIG. 6 shows only the majorcomponents related to the location registration procedure, the ISR, andthe update of the voice service configuration information according tothis embodiment. Further, although not shown, the MME 31 may include anISR control unit that is the same as an ISR control unit 321 in FIG. 6.

The ISR control unit 321 performs signalling necessary to start the ISRwith the mobility management node (e.g., the MME 31) of another RAT.Further, the ISR control unit 321 performs signalling necessary to startthe ISR with a transfer node such as an S-GW and with a subscriberinformation server such as an HSS.

Further, the ISR control unit 321 sends a location registration response(i.e., RAU accept) indicating “ISR deactivated” to the mobile station 1in response to receiving, from the mobile station 1 when the ISR isactivated, a location registration request (i.e., RAU request)indicating the update of the voice service configuration informationstored in the mobile station 1.

FIG. 7 is a flowchart showing an example of the operation of the ISRcontrol unit 321. The procedure of FIG. 7 is initiated when the ISR isactivated (Step S21). In Step S22, the ISR control unit 321 determineswhether a RAU request is received or not. When the RAU request isreceived, the ISR control unit 321 determines whether the RAU requestindicates the update of the voice service configuration information(VSC) or not (Step S23).

When the RAU request does not indicate the update of the voice serviceconfiguration information (VSC), the ISR control unit 321 continues theISR activated state and sends a RAU accept indicating “ISR activated” tothe mobile station 1 which sent the RAU request (Steps S24 and S25). Thecase where the RAU request does not indicate the update of the voiceservice configuration information (VSC) is, for example, when thereceived RAU request is a normal periodical RAU request.

On the other hand, when the RAU request indicates the update of thevoice service configuration information (VSC), the ISR control unit 321determines to deactivate the ISR and sends a RAU accept not indicating“ISR activated” to the mobile station 1 which sent the RAU request(Steps S26 and S27).

Third Embodiment

The first embodiment describes two examples of the scheme that theupdated content of the voice service configuration information in themobile station 1 is synchronized between the MME 31 and the SGSN 32. Forthe example 1, an illustrative sequence is shown in FIG. 3 in the firstembodiment. In the third embodiment, an illustrative sequence for theexample 2 is described. Note that the configuration of the mobilecommunication system according to the third embodiment may be the sameas the configuration example shown in FIG. 1.

FIG. 8 is a sequence chart showing one example of the procedure toachieve synchronization of the voice service configuration informationVSC updated in the mobile station 1 between the MME 31 and the SGSN 32.FIG. 8 is different from FIG. 3 in Steps S310 and S312.

The example of FIG. 8 corresponds to the case where the mobile station 1informs neither the MME 31 nor the SGSN 32 about ISR deactivation. Thus,in Step S310, the mobile station 1 does not perform an explicit localISR deactivation. Specifically, the mobile station 1 (i.e., thecommunication control unit 11) maintains the TIM as “RAT-related TMSI”corresponding to ISR activated. This is for the purpose of not informingthe MME 31 about ISR deactivation in the later step S312.

However, the mobile station 1 (i.e., the communication control unit 11)memorizes that the voice service configuration information VSC has beenupdated (in Step S106) but another RAT (i.e., the MME 31) related to theISR has not been notified of the update. Specifically, while the mobilestation 1 (i.e., the communication control unit 11) does not performexplicit ISR deactivation that triggers a notification to the network(i.e. the MME 31 and the SGSN 32), it performs implicit ISR deactivationthat does not trigger a notification to the network. Thus, thecommunication control unit 11 (i.e., the LTE control unit 111) sends aTAU request to the MME 31 corresponding to the E-UTRAN 21 to which themobile station 1 moves in Step S312. This TAU request contains anotification about the update of the voice service configurationinformation VSC, just like the RAU request in Step S107.

In the example shown in FIG. 8, the mobile station 1 does not need toinform the network (i.e., the MME 31 and the SGSN 32) about ISRdeactivation. Further, in the example shown in FIG. 8, the MME 31 andthe SGSN 32 can synchronize the updated content of the voice serviceconfiguration information in the mobile station 1 with each otherwithout signalling for context resynchronization.

Other Embodiments

In the first to third embodiments, a combined system of 3GPP UMTS andEPS (Evolved Packet System) is specifically described. However, thetechnical ideas described in those embodiments can be applied generallyin a mobile communication system that accommodates a plurality ofdifferent RAN/RAT, allows reselection between different RAN/RAT and hassimilar scheme as the ISR for reducing signalling in locationregistration caused by the reselection. For example, the first to thirdembodiments can be applied also to a mobile communication system thataccommodates 3GPP RAT and non-3GPP RAT (e.g., WiMAX, IEEE802.16m).

Further, the first to third embodiments can be combined as appropriate.Furthermore, the invention is not limited to the embodiments describedabove, and it will be obvious that various modifications may be madetherein without departing from the spirit and scope of the presentinvention described above.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2012-14020, filed on Jan. 26, 2012, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   1 MOBILE STATION-   3 CORE NETWORK-   10 RADIO COMMUNICATION UNIT-   11 COMMUNICATION CONTROL UNIT-   21 E-UTRAN (EVOLVED UNIVERSAL TERRESTRIAL RADIO ACCESS NETWORK)-   22 GERAN (GSM EDGE RADIO ACCESS NETWORK)/UTRAN (UNIVERSAL    TERRESTRIAL RADIO ACCESS NETWORK)-   31 MME (MOBILITY MANAGEMENT ENTITY)-   32 SGSN (SERVING GPRS SUPPORT NODE)-   111 LTE (LONG TERM EVOLUTION) CONTROL UNIT-   112 2G/3G CONTROL UNIT-   321 ISR (IDLE MODE SIGNALLING REDUCTION) CONTROL UNIT

1-61. (canceled)
 62. A mobile station comprising: a transmitterconfigured to send an RAU (Routing Area Update) Request message; areceiver configured to receive a RAU ACCEPT message in a case where theRAU Request message is accepted; and a controller configured to set aTIN (Temporary Identity used in Next update) to “P-TMSI(Packet-Temporary Mobile Subscriber Identity)” in a case where (1) themobile station had initiated a routing area update procedure due to achange in a “UE's (User Equipment) usage setting” or a “Voice domainpreference for E-UTRAN (Evolved Universal Terrestrial Radio AccessNetwork),” and (2) the RAU ACCEPT message contains an indication of ISR(Idle mode Signaling Reduction) being activated.
 63. The mobile stationaccording to claim 62, wherein the processor configured to set the TINto the “P-TMSI” in a case where (1) the mobile station had initiated therouting area update procedure due to the change in the “UE's usagesetting” or the “Voice domain preference for E-UTRAN,” and (2) the RAUACCEPT message contains the indication of ISR being activated, and (3)the TIN is not currently set to the “P-TMSI”.
 64. The mobile stationsystem according to claim 62, wherein the processor configured to setthe TIN to the “P-TMSI” in a case where (1) the mobile station hadinitiated the routing area update procedure due to the change in the“UE's usage setting” or the “Voice domain preference for E-UTRAN,” and(2) the RAU ACCEPT message contains the indication of ISR beingactivated, and (3) the TIN is currently set to RAT-related TMSI (RadioAccess Technology related Temporary Mobile Subscriber Identity).
 65. Themobile station according to claim 62, wherein the setting of the TIN tothe “P-TMSI” identifies that the status of ISR activation in the mobilestation is deactivated.
 66. The mobile station according to claim 62,wherein the “UE's usage setting” indicates whether the mobile stationbehaves in a voice centric or data centric way.
 67. The mobile stationaccording to claim 62, wherein the “Voice domain preference for E-UTRAN”indicates whether the mobile station is configured as CS (CircuitSwitched) Voice only, CS Voice preferred and IMS (IP MultimediaSubsystem) PS (Packet Switched) Voice as secondary, IMS PS Voicepreferred and CS Voice as secondary, or IMS PS Voice only.
 68. Themobile station according to claim 62, wherein the RAU ACCEPT messagecorresponds to the routing area update procedure initiated by the mobilestation.
 69. A mobile station comprising: a transmitter configured tosend an TAU (Tracking Area Update) Request message; a receiverconfigured to receive a TAU ACCEPT message in a case where the TAURequest message is accepted; and a controller configured to set a TIN(Temporary Identity used in Next update) to “GUTI (Globally UniqueTemporary Identifier)” in a case where (1) the mobile station hadinitiated a tracking area update procedure due to a change in a “UE's(User Equipment) usage setting” or a “Voice domain preference forE-UTRAN (Evolved Universal Terrestrial Radio Access Network),” and (2)the TAU ACCEPT message contains an indication of ISR (Idle modeSignaling Reduction) being activated.
 70. The mobile station accordingto claim 69 wherein the processor configured to set the TIN to the“GUTI” in a case where (1) the mobile station had initiated the trackingarea update procedure due to the change in the “UE's usage setting” orthe “Voice domain preference for E-UTRAN,” and (2) the TAU ACCEPTmessage contains the indication of ISR being activated, and (3) the TINis not currently set to the “GUTI”.
 71. The mobile station systemaccording to claim 69, wherein the processor configured to set the TINto the “GUTI” in a case where (1) the mobile station had initiated thetracking area update procedure due to the change in the “UE's usagesetting” or the “Voice domain preference for E-UTRAN,” and (2) the TAUACCEPT message contains the indication of ISR being activated, and (3)the TIN is currently set to RAT-related TMSI (Radio Access Technologyrelated Temporary Mobile Subscriber Identity).
 72. The mobile stationaccording to claim 69, wherein the setting of the TIN to the “GUTI”identifies that the status of ISR activation in the mobile station isdeactivated.
 73. The mobile station according to claim 69, wherein the“UE's usage setting” indicates whether the mobile station behaves in avoice centric or data centric way.